The present invention relates to a signature stacker and, particularly to an apparatus for pushing a stack of signatures from the stacker.
A known stacker which stacks folded signatures is disclosed in U.S. Pat. No. 4,547,112. The stacker includes a temporary signature holding assembly, a revolvable turntable and a pusher assembly. The temporary signature holding assembly collects a temporary stack of signatures from a continuous infeed supply while the pusher moves a completed stack from the turntable or while the turntable is revolving to alternate the fold location. This permits the infeed supply to continue without disruption.
The temporary signature holding assembly is disposed directly above the turntable. The temporary signature holding assembly pivots downwardly from a collecting position to allow the temporary stack to fall onto the center of the turntable. The temporary signature holding assembly then returns to the collecting position. When a stack has the desired number of signatures, the pusher is actuated to push the stack onto a delivery table.
The stacker can stack signatures of various widths. The pusher assembly of the known stacker has a single travel length regardless of the width of the signatures. The pusher is designed to have a long travel to push the longest width stack from the stacker and onto the delivery conveyor. Therefore, when relatively large width stacks are pushed, the pusher assembly must cycle through the long travel. This results in wasted pusher motion and cycle time because the temporary signature holding assembly cannot drop signatures onto the platform until the pusher completely returns to a starting position which will not interfere with the falling of signatures onto the turntable.